This invention relates to an improved process for production of alkenes from halogenated organic compounds. More specifically, this invention relates to a process for dehydrohalogenation of halogenated organic compounds using a staged upflow reactor.
Dehydrohalogenation of halogenated organic compounds is generally conducted in the liquid phase by mixing a halogenated alkane or halogenated alkene with a strong base in a solvent. Because the base is usually added as an aqueous solution, phase transfer catalysts are often employed to promote contact of the reactants.
In many processes a series of continuous stirred tank reactors are used and by-products of the reaction, as well as unreacted starting materials, are removed by steam stripping or distillation. For example, 2-chloro-1,3-butadiene can be prepared by dehydrohalogenation of 3,4-dichlorobutene-1 in a series of co-current continuous stirred tank reactors using the catalytic process disclosed in U.S. Pat. No. 3,981,937. Other processes involve the use of boiling reactors, for example as disclosed in U.S. Pat. No. 3,772,461, or in stirred tanks coupled with phase decantation as disclosed in U.S. Pat. No. 4,418,232. Each of these methods is associated with disadvantages. The stirred reactor processes suffer from relatively low conversions and result in production of high levels of organic waste. Conversions in one-pass boiling reactor processes are typically extremely low, for example 85% or less. In addition, investment and energy costs associated with such processes are high.
Dehydrohalogenation processes that result in improved reactant conversion levels would result in production of lower levels of organic waste. These more efficient processes reduce production of halogenated organic compounds that can contribute to global warming. In addition, energy and material consumption are reduced.
The present invention is directed to an improved process for dehydrohalogenation of organic compounds. In particular, the present invention relates to a process for dehydrohalogenation of a halogenated compound selected from the group consisting of halogenated alkanes and halogenated alkenes, said process comprising
A) contacting a first composition comprising said halogenated compound with a second composition comprising a base having a Kb of at least 10xe2x88x929, in the liquid phase, in a reactor having multiple stages, at a temperature sufficient to initiate the exothermic reaction of said halogenated compound with said base, thereby forming a dehydrohalogenated compound having a boiling point lower than that of said halogenated compound; and
B) maintaining the temperature of the reactor contents at a temperature sufficient to vaporize said dehydrohalogenated compound thereby causing agitation of said reactor contents and transfer of vaporized dehydrohalogenated compound through said multiple stages of said reactor, said vaporization providing a means of agitation.